Charging Camper Batteries: Using Your Truck's Power

how to charge camper batteries with truck

Charging a camper battery with a truck is a great way to top it off when boondocking without electrical hook-ups. This can be done by using the truck's alternator, as long as there is a 7-pin travel trailer plug. However, it is important to note that the charge will be slow, as the truck's starting battery takes priority and there is only a little power left for the camper battery. To increase the charging speed, a DC to DC charger can be installed, which boosts the voltage and amps coming from the alternator. This modification requires some electrical knowledge and tools but can be a worthwhile investment for those who frequently boondock.

Characteristics Values
Camper battery charging methods Truck alternator, generator, solar power, wind power, shore power
Camper battery types Wet cell, AGM, lithium iron phosphate
Camper battery maintenance Check temperature, insulate battery compartment, buy a battery warming system
Camper battery monitoring Xantrex Linklite, Trimetric TM-2030

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Camper batteries can be charged using the truck's alternator

The best alternators are those that produce a lot of amperage, like those found in heavy-duty trucks (160 amps is the norm). The quality of the charge can be improved by upgrading the existing charge wire from the 12-gauge wire you typically find in your RV to an 8-gauge or larger wire. You can also ensure a battery isolator is wired into the circuit to prevent the batteries in your RV from draining.

It's important to note that the distance between the vehicle battery/alternator and the camper battery is too far to fully charge a trailer battery from a depleted state. The most you can do is provide a maintenance charge to prevent your trailer battery from dying.

To charge your trailer battery, you'll need a DC-to-DC battery charger. These chargers typically connect directly to your batteries to provide the power needed to charge your trailer battery from a depleted state. Many models are designed to draw power from both your vehicle alternator and solar panels, if available.

  • Determine a location to install the DC-to-DC battery charger unit as close to the RV's house/service battery as possible. Make sure the area is watertight and allows for as much airflow as possible.
  • Install the input wire from the starting battery to the charger. Thread enough wire from the positive terminal on the starting battery to the positive input terminal on the DC-to-DC charger, leaving some wiggle room.
  • Ground the input terminal. Since the starting battery's negative terminal is grounded to the chassis of the vehicle, do the same for the input terminal on the charger.
  • Ground the output wire from the charger to the 7-way connector. Use 10-12-gauge wire and a T-tap splicer to connect the negative wire from the charger to the 7-way connector's neutral wire.
  • Connect the D+ wire to the unit. 18-gauge wire will suffice for this.
  • Select the charging voltage switches on the charger, depending on the type of house/service battery you have. Refer to the manual that came with your charger to determine the setting specific to your battery type.
  • Install and secure the DC-to-DC charger to the vehicle. It can be mounted vertically or horizontally, but it should not move around while the vehicle is in motion.
  • Make all wired connections to the battery charger: Positive Input, Neutral Input, Positive Output, and Neutral Output. If there is already a 10-12-gauge wire going through to the 7-way connector, you can use that wire to connect the charger's output positive terminal. Install an inline fuse between the charger and the 7-way.
  • Connect the D+ wire from the charger to the vehicle's fuse box. Since the charger turns on any time it detects a 12V current, it needs to know when you've turned on/off the ignition of the vehicle so as not to drain the starting battery when the engine is off. Identify a fuse connected to the ignition and thread an 18-gauge wire directly from the D+ input on the charger to the fuse box.
  • Attach the positive input wire to the positive terminal of the starting battery. This is the final step, so make sure all wiring is secure downstream of the starting battery, and all ground wires are in place.
  • Start the engine and make sure the DC-to-DC battery charger turns on. You can use a simple voltage meter to check the voltage coming from the starting battery into the charger, as well as the voltage going out of the charger to the RV house/service battery.
  • Finally, check the house/service battery bank voltage before and after running the engine to ensure all is working properly.

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A DC-to-DC battery charger can be used to speed up charging

A DC-to-DC battery charger acts as a pump to boost the voltage and amperage supplied to the trailer's battery, providing a more powerful charge and greatly reducing charging time. The maximum amperage with a DC-to-DC battery charger is around 20 amps, compared to just 5 amps with a trickle charge.

To install a DC-to-DC battery charger, you will need to connect the input wire from the truck's starting battery to the charger, ground the input terminal, and then connect the output wire from the charger to the 7-way connector. You will also need to connect a D+ wire to the unit and select the appropriate charging voltage switches for your battery type. Finally, mount the charger securely in your vehicle, ensuring that it does not move while the vehicle is in motion.

It is important to note that not all trucks are capable of charging trailer batteries while driving, and some may require modifications such as larger battery wires or voltage-boosting gismos. Additionally, always monitor your trailer battery's charge to ensure it does not drop below 50%, as this can shorten the lifespan of the battery.

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Charging via the truck's alternator is slow

Charging camper batteries via the truck's alternator is slow. This is because the alternator is a mechanical device with lots of moving parts. The harder you work your alternator, the sooner it will fail. If your alternator stops working, so does your engine until you replace it.

The alternator's job is to keep the starting battery full. The starting battery powers all of the electrical devices that your vehicle needs on a day-to-day basis. When you convert a van into a camper van, you install 'house' batteries to run household stuff like lights, fans, refrigerators, computers, and such.

The truck's alternator can charge the camper batteries, but only with a trickle charge. This is because the camper batteries are several feet downstream. The truck engine battery gets a quick charge, and the voltage peaks, but the trailer battery does not get enough voltage to boost its charge much.

If you have a 7-way connector between your towing vehicle and your RV, your vehicle's starting battery powers these items as well. Therefore, the RV's battery bank is only able to get a little bit of power.

If you want to charge your camper batteries more effectively, you can install a DC to DC battery charger. This acts like a pump to electronically boost the voltage and amperage coming from the starting battery to provide a more powerful charge to the camper batteries.

Another option is to use a battery isolator, which connects your house battery bank to your starting battery. When you turn off your engine, the isolator isolates the two battery banks so that when you use your lights, fans, refrigerator, etc., you won't kill your starting battery.

A third option is to use a battery to battery (B2B) charger, which takes the voltage and amperage that is being put out by the vehicle alternator and regulates the amperage down to a modest pre-set level and boosts the voltage as necessary to fully charge any batteries. This lowers the strain on your alternator and gives you a solid number to work with when determining how many amps the charger will operate at.

In summary, charging camper batteries via the truck's alternator is slow because the alternator has a limited lifespan that is shortened by hard work, and the camper batteries are too far downstream to get a full charge. There are alternative options for charging camper batteries, such as a DC to DC battery charger, a battery isolator, or a B2B charger.

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A generator can be used to charge camper batteries

The old single-stage converter/chargers got a bad rap, and rightly so, but today's 45 and 55-amp converter/chargers are much better. They work in place of your batteries by providing a constant 13.6-volt DC output. They also distribute 110-volt AC power and provide automatic three-stage charging for your batteries when needed. Many units also provide AC and DC branch distribution.

Generators work great at recharging your batteries, but not all are good for camping. Industrial generators are relatively cheap and provide lots of wattage, but they are also big, heavy, and extremely noisy. Few things irritate campers more than a neighbour's noisy generator.

Fortunately, there are several low-noise, camping-friendly generators on the market today. These are not only light but are also extremely quiet. The big negatives associated with generators are that they must be stored, taking up valuable storage space, generate deadly carbon monoxide, and can easily be stolen. Make sure to keep them chained up at all times when camping within sight of strangers.

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Solar power is another charging option

Overcast skies and shading can reduce the effectiveness of solar power, and there is a high initial cost to set up. However, this cost can be reduced by buying a starter kit and doing the installation yourself.

If you're interested in solar power, it's worth checking out a Renogy 100-watt solar power starter kit and reading the article "Building a Great Solar Powered Truck Camper Rig" for more information on how to build a solar power system for your camper.

Frequently asked questions

You can charge your camper battery with your truck by using your truck's alternator. This method will only provide a small trickle charge to your camper battery, so it is recommended to use a DC-to-DC battery charger to boost the voltage and amperage.

Charging a camper battery with a truck can take a long time, as the truck's alternator has to power the truck's electronics and lights, in addition to charging the camper battery.

A DC-to-DC battery charger boosts the voltage and amperage coming from the truck's alternator, providing a faster and more powerful charge to the camper battery.

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